Melting systems for bags convert a solid working material packaged in a packaging bag, such as a hot melt adhesive, from its initial solid to a flowable state by heating it in a cylindrical receiving chamber of a pressing unit while a pressing plunger is advanced in the receiving chamber from the rear bag end so that molten working material is pressed out and the packaging bag is gradually compressed in axial direction along the cylindrical wall of the receiving chamber. The pressing plunger is provided with a stripper plate to facilitate low-friction backward reloading of new filled packaging bags without a major cleaning effort. It primarily has a sealing function towards the inner cylinder wall and serves as stripper for any working material that may adhere to the inner cylinder wall that undesirably came between the outside of the packaging bag and the inner side of the cylinder wall. A low friction value between the stripper plate and the inner cylinder wall is desired to allow a precisely predefined discharge quantity, i.e. dosage, of the molten working material. For these and other reasons, a preferred stripper plate is typically made of an elastically resilient material such as a plastic, in particular, PTFE (such as Teflon®) and the cylindrical inner wall is also coated with a similar low-friction sliding material. Varying processing temperatures, in particular hot and cold zones in a bag melting system, result in varying calibers of the stripper plate in proportion to the respective temperature. It is therefore difficult, especially in bag melting systems, to ensure uniform force and sealing conditions between the stripper plate and the cylindrical inner wall over the entire pressing path.